1. Department of Electric Power Engineering, Hebei Key Laboratory of Green and Efficient New Electrical Materials and Equipment, North China Electric Power University, Baoding 071003, P. R. China
2. Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China
3. Gui Zhou Mei Ling Power Sources Co. Ltd, State Key Laboratory of Advanced Chemical Power Source, Zunyi, Guizhou 563003, China